Method of and apparatus for the manufacture of tin plate



June 16, 1931. s. E. DIESCHER 1,810,699

METHOD OF AND APPARATUS FOR THE MANUFACTURE OF TIN PLATE Filed Dec. 5, 1925 3 Sheets-Sheet 1 Jam;

June 16, 1931. s. E. DIESCHER 1,810,699

METHOD OF AND APPARATUS FOR THE MANUFACTURE OF TIN PLATE Filed Dec. 5, 1925 3 Sheets-Sheet 2 N A f, w m E Cj 3] Q) Q -g June 16, 193 s. E. DIESCHER METHOD OF AND APPARATUS FOR THE MANUFACTURE OF TIN PLATE 5. 1925 5 Sheets-Sheet 3 Filed Dec.

fZZ/A Patented June 16, 1931 UNITED STATES PATENT OFFICE SAMUEL E. DIESCHER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 S. DIESCHER & SONS, OF PITTSBURGH, -PEN'NSYLVANIA, A (JO-PARTNERSHIP CONSISTING- OF SAMUEL E. DIESCHER- AND AUGUST 1?. DIESCHER METHOD OF AND APPARATUS FOR THE MANUFACTURE OF TIN PLATE Application filed December The invention relates to the manufacture of tin plate generally, but is particularly applicable to the manufacture of what is commonly known as coke, plate, which is that having a thin coating of tin. Ordinarily the thickness of the coating is designated by the amount of tin used inplating both faces of 31,360 square inches of plate, which is a base box. The tin actually consumed in plating is therefore called the yield and a low commercial yield heretofore obtained under practical working conditions has been about one and one-half pounds of tin per base box. For What is known as charcoal plate, thatis to say plate having a relatively thick coating of tin the ield is materially higher.

The 0 j ect of this invention is to provide a method of and apparatus for producing tin plate having a high luster, regardless of Whether it is coke or charcoal plate, but more particularly for rapidly producing coke plate having a high luster,'free from defects, and at a low yield The invention may be best understood by first explaining the efiects of certain prevailing conditions in the manufacture of tin plate. As is Well known, plates to be coated are delivered to a tin pot submerged in tanks of slightly acid water to prevent their oxidation. While wet, they are passed into and through a body of flux and then the molten tin contained in the tin pot to which heat is continuously applied. At the entering end of the tin pot a body of flux, laterally confined ;in a suitable flux box, rests upon the molten tin, and the plates to be coated pass through this flux before entering the tin bathf Supported upon the tin-bath at the discharge side of the pot there is a body of palm oil having arranged in it aseries ofpairs of, tinning and polishing rolls arranged .in vertical alignment between which the plates pass as they emerge from the tin bath.

In some cases plates are manually fed into and through the tin bath and into the bite of the first pair of tinning rolls in the'palm oil. These rolls are ordinarily several times as long as the width of plates being tinned, and accordingly a workman using a forked rod is obliged to feed the plates in such a 5, 1925. Serial No. 73,379.

mannerthat a plurality of lines or strands of them pass through the tinning apparatus side by side. It is necessary for the workman to feed the entering end of a plate quite rapid- 1y through the tin bath so that he can keep each line of plates continuously passing through the tin bath at close intervals. As soon as the entering end of a plate is engaged by the tinning rolls the travel of the plate is at a much slower rate than that at which it was fed into the bite of the rolls. The net result of this is that the rear end of each plate is in the tin bath for a materially longer time than its forward end, and, because the thickness of coating depends in part upon the length of time a plate is in the tin bath, the consequence is that the plate is not uniformly coated. To obtain fair results as far as concerns uniformity of coating it is necessary to rotate the tinning rolls of hand fed niachines quite slowly.

In other cases plates are fed into the tin bath by a air of continuously rotating rolls. When so ed, the plates may be withdrawn at a considerably higher rate of speed than in the case of hand feeding, because when mechanically fed every portion of each plate passes through the tin bath at thesame rate of speed and'remains in the tin bath for the same length of time, which is sufficient to permit the plate and the chilled tin adhering to it to become sufiiciently heated for proper removal of molten tin b the tinning rolls for the production of 00 e plate. It therefore follows that coke e plates are mechanitall-y fed into the bath than when manually One of the prejudicial conditions incident to the production of tin plate is the presence of tin oxide which forms in the tin bath, and, being lighter than molten tin, floats upon its surface. Tin oxide is formed chiefly at the entering sideof a tin pot by contact of the molten tin with air on the surface of the bath and air carried into the fluxand'bath by the wet entering plates. This tin oxide has a tendency to cling to the plates and mar their surface coatings.

A further prejudicial condition incident plate may be more rapidly produced when t to the production of tin plate is the presence of chilled tin in thebath adjacent to the flux. It is here where the cool wet. plates to be coated enter the molten tin after passing through the flux, and they of course withdraw heat from andchill the tin. This chilling is effected in part by the temperature of the plates and the water adhering to them, and in part by the latent heat consumed in vaporizing the water, it being understood that the temperature of the molten tin is approximately 575 F. The chilling of the tin is so great that not infrequently it'is necessary to periodically remove masses of solidified, or partially solidified, tin from the surface of the bath adjacent to the flux, Furthermore, the chilling of tin adjacent to 'the flux is much greater when plates are mechanically fed into and through the tin than when manually fed, because, when mechanically fed, they enter and pass through the tin bath at a uniform rate of speedwhich is materially lower than that at which the plates are manually fed, and accordingly the maximum heat absorption for mechanically fed plates is at the entering end of the bath where the plates contact with the tin adjacent to the flux for a much longer period of time than do manually fedplates. This chilled tin as well as the tin oxide,,produced as explained above, interferes with, and is projudicial to, the tin plating operation.

A still further prejudicial condition incident to the production of tin plate "is the presence of particles of tin-iron alloy in the molten tin. At times a tinvbath is substantially saturated with these particles. The tin-iron alloy is formed largely, if not entirely, by the attack of the molten tin upon the pot and upon its contained apparatus, all of which are made of cast iron or steel. As plates pass through the tin bath, particles of tin-iron alloy adhere to them resulting in a diminution of the luster of the coated plates, particularly when coke plate is being produced. Furthermore, tin-iron alloy has a higher melting point and is slightly heavier than pure tin, and accordingly the particles of tin-iron alloy adhering to the plates are more solid than the tin. Therefore, when plates pass through the tinning rolls at the discharge side of the pot the rolls cannot, regardless of the fluidity of the tin'itself, thin the coatin of tin to the thickness obtainable were t e tin-iron alloy absent. In other words, these hard or substantially hard particles of tin-iron alloy adhering to the plates spread the tinning rolls to the extent of the greater resistance of the tin-iron alloy against compression and render the tinning rolls incapable of thinning the coating below the thickness effected by these adhering particles. Hence it is due to the presence of a substantial, but changeable amount of tiniron alloy in the tin bath that coke plate having constantly a uniform low yield has been incapable of practical commercial production. Stated more specifically, the chief object of this invention is to provide a method of and apparatus for eliminating from a tin bath the several prejudicial conditions explained above, to the end that coke plate having a low yield, greater uniformity of thickness of coating, and a high luster may be rapidly produced. Other objects of the invention will appear in the ensuing description of it.

In the practice of this invention provision is made for the removal of the chilled tin, tin oxide and tin-iron alloy from the path of the tin plates through the tin bath.' In doing this an important step in the procedure consists in causing the bath of molten tin to flow in a cycle. The flow of the tin bath is preferably effected by so constructing the tin pot and the instrumentalities for heating it, and by so applying heat to the tin pot, that a convection current is set up in the molten tin causing it to flow upwardly beneath the flux at the entering end of thepot, then laterally in the general direction of the passage of plates through the bath, and then downwardly and rearwardly towards and to the bottom portion of the pot'beneath the flux. I have discovered that, by causing the molten tin to flow in such a cycle, the small particles of tin-iron alloy suspended in it become to a large extent deposited in the chilled tin and the tin oxide beneath the flux. Although tiniron alloy is slightly heavier than molten tin, I have found that it does not sink to the bottom of the bath of tin until it has accumulated in relatively large particles and until the tin bath is substantially saturated with it. By causing this convection current cycle of flow in the tin bath, and entraining the particles of tin-iron alloy in the mass of chilled tin and tin'oxide, and removing this mass from the path of the plates, the particles of tin-iron alloy are eliminated from the bath as they are formed, and accordingly do not accumulate to an extent suflicient to prejudici'ally effect the operation.

- At the surface of the tin bath adjacent to the flux provision is made for causing the mixture of chilled tin and tin oxide, and also the tin-iron alloy when deposited in it, to move laterally and to become segregated at a point for removal from the bath. I have found that this may be done by arranging a rollin the tin bath adjacent to the ath of the entering plate in such position t at the upper portion of t e roll protrudes somewhat above the surface of the molten tin, and by rotating this roll so that its side adjacent to the path of the entering plates moves from such path. The layer of chilled tin and its content of impurities floating upon the surface of the tinbath is in the nature of a thin adherent scum, and is picked up by the portion of the roll protruding above the surface of' the tin and carried to the surface of the bath on the opposite side of the roll.

The mass-or scum floating on the bath is somewhat porous and is much lighter than the pure molten tin. Whether it is due to these characteristics of the mass, or to some other cause, I have found that, as the protruding portion of the roll enters the tin bath, the layer of chilled tin and the impurities mixed with it adhering to the roll are floated off by the heavier molten tin and accumulate in a body which floats upon the surface of the tin in a position to be readily ladled off. The rotation of this protruding roll not only takes up and moves laterally the skin of chilled tin and impurities adjacent to it, but, due to the cohesion of this mass the rotation of the roll causes it to move as a layer upon the surface of the tin beneath the flux.

In a similar manner provision is made for the segregation and removal of chilled tin and such impurities as may be mixed with it which form upon the surface of the bath beneath the palm oil at the discharge side of the pot. However, in the practice of this invention, it has been found that a very small amount of impurities form upon this surface of the bath.

In case the mass of chilled tin and impurities mixed with it are not removed by causing thesurface of the metal to continuously flow laterally, as for example when the skimming machinery fails, the tin-iron alloy may be removed from the molten tin by permitting it to accumulate in particles of such size that they will sink. to the bottom of the tin pot, and by so shaping the bottom of the pot that these particles will flow into a well from which an accumulation of them may be periodically removed. However, this practice ,does not produce plates of as high quality as when the accumulated mass of chilled tin and impurities is continuously removed from the surface of the bath.

The invention will be further explained, and other features of it described, in connection with the explanation of the accompanying drawings which show apparatus embod ing the invention and for the practice'of it. In the drawings, Fig. 1 is a vertical central sectional view through a tin pot and the feeding and coating mechanism mounted in it; Fig.2 a plan view of the pot and mechanism shown in Fig. 1; Fig. 3. a vertical sec tional View taken on the lin e-'III-III, Fig. 2; and Fig. 4 a vertical central sectional view through the tin pot and the heating furnace beneath and around it, the guiding and coating mechanism of the pot being removed.

The invention is illustrated in its applicability to a single strand tinning apparatus, and is preferably so practiced. However, it is also applicable to multiple strand and to duplex apparatus.

The pot comprises a front wall 1 at its entering side, a rear wall 2 at its discharge side, side walls 3 and 4, a bottom 5, and a transverse vertical partition 6, which, with the rear wall 2 .and portions of the'side walls, form a chamber for the reception of palm oil, or in other words the grease pot. The level of the molten tin in the entering side of the pot is indicated by the dot-and-dash line 7, and on the discharge side of the pot by a similar line 8, while the upper level of the oil in the grease pot is indicated by a dotand-dash line 9. At the entering side of the pot a body of flux 10 rests upon the molten tin and is laterally confined by a flux box 11. Arranged above the flux box and in a position to direct plates downwardly through the flux, there are a pair of feed rolls 12 into the bite of which plates to be coated are placed in any desired manner. These rolls are rotated at a uniform rate of speed to feed plates downwardly through the flux and into the tin where they. are caught by a guide 13 which directs them into the bite of a pair of feed rolls 14 rotated at the same peripheral speed as rolls 12. The rolls 14 are purely feed rolls, and their use may be dispensed with in casev the plates being coated are of such length that their forward ends are engaged by the tinning rolls before their rear ends pass beyond feedrolls 12;

Beyond feed rolls 14 there is a guide 15 for directing the plates upwardly into the bite .of the tinning rolls Two pairs of tinning rolls 16 and 17 are arranged in vertical align ment in the grease pot, and above the tinning rolls there is a pair of polishing rolls 18. Bearing upon'the lower portions of the tinning and polishing rolls there are wipers 19, 20 and 21, the purpose of which is well known to those skilled in the art. Above the polishing rolls there are a pair of guides 22 which direct the plates intothe bite of suitable catcher rolls 23. The guide rolls 12 and 14, guide 13 and flux box 11 are all mounted in a suitable frame 25 supported by the tin pot, and in a similar manner the mechanism in the grease pot is mounted in a frame 26 also supported by the pot. moved in the customary manner when necessary or desirable.

Driving connections are'provided for. rotating all of the feeding, tinning and polishing rolls at a uniform peripheral speed, which, however, may be varied. As generally indicated in Fig. 2, a power shaft 30 may be arranged adjacent to'side wall 3 of the pot, and from it driving connections may be made with the several pairs of rolls. For driving the lowermost of the pair of feed rolls 12, one of itsends may be provided with a sprocket 31 connected by a chain 32 to a sprocket 33 mounted on a shaft 34 provided with a bevel gear 35 meshing with a bevel pinion 36 connected to power shaft 30. The

Both of these frames may be reuppermost feed roll 12 is suitably urged toward the lowermost roll and is accordingly driven by friction. The other end of this driven feed roll 12 is provided with a bevel pinion meshing with a similar pinion 41 mounted on a shaft 42 provided with a worm 43 for driving the lowermost of the pair of feed rolls 14 in the tin bath. The upper feed roll 14 bears upon the lower roll and is accordingly driven by friction.

For driving the pairs of tinning and polishing rolls in the grease pot, shaft 30 may be provided with a worm 45 for driving a shaft 46 provided with a pinion 47 adapted to slide upon shaft 46 into mesh with a pinion 48 borne by the left hand polishing roll 18. Through thetrain of pinions generally illustrated in Fig. 1, the pairs of tinning rolls 16 and 17 are rotated.

It has been previously explained that a roll or rolls are provided in the surfaceiof the tin bath for causing the chilled tin and accumulation of impurities to move laterally and become segregated for removal from the bath. At the entering end of the pot, and somewhat to the right .of the path of the plates passing through the flux, there is a roll 50, the upper portion of which protrudes above the level of the molten tin indiicated by line 7. This roll may be con' tinuously rotated by a worm 51 (Fig. 2) borne by shaft 42 and meshing with a worm wheel 52 at the outer end of roll 50, the direction of rotation of roll being as indicated by the arrow on it in Fig. 1. In cases where itis necessary to do so, as for example when operating the coating apparatus at a above the metal line 8. This roll may be continuously rotated in the direction of the arrow shown on it in Fig. 1 by means of a sprocket chain drive between it and the tinning roll 16 adjacent to it. As shown in Fig. 2 theouter end of roll 54 is provided with a sprocket wheel 55, and the outer end ofthe left hand tinning roll 16 with a sprocket wheel 56, the two being connected by a chain 57.

As previously explained, the invention contemplates causing the molten metal to flow in a cycle by setting up a convection current in it. To this end provision is made for heating the entering side of the pot to a greater extent than the discharge side, for regulating the difference in temperature between the entering and discharge side of the pot, and for effecting heat radiation from a large portion of the outer walls of the discharge side of the pot,particularly from the Walls of the grease pot.

As shown in Fig. 4, the tin pot preferably rests, in a manner presently to be explained, upon the tops of furnace walls which form two heating chambers, a chamber beneath the entering side of the pot and a chamber 61 adjacent to the rear of the grease pot. A fuel burner 62 is arranged in the bottom of heating chamber 60, and the flames and products of combustion from it normally pass upwardly and first heat the entering side of thepot. From the upper portion of chamber 60 the products of combustion pass through ports 63, arranged one on each side of the pot as shown in Fig. 3,, and flow into chamber 61 where their residual heat heats the rear wall of the grease pot, but to a less extent than the heating of the entering end of the pot. Between heating chambers 60 and 61 there is a by-pass 64 having its inlet'directly opposite to and in line with burner 62, and through which flow of flames directly from burner 60 into heating chamber 61 1s controlled bya suitable slide valve 65. By varying the position of valve 65, the heating effect of the gases in chambers 60 and 61 may be varied as required. The products of combustion from chamber 61 flow downwardly through a passage 66 to a tunnel 67. leading to a suitable stack, and their flow through passage 66 may be controlled by a slide valve 68 similar to Valve65.

The customary manner of mounting a tin pot upon a furnace is to provide the bottom of the pot with laterally extending flanges which rest upon the hottest portions of the furnace walls in the plane of the bottom of the pot and in a position to become burned out both by the heat of the furnace walls and of the products of combustion which flow above the flanges at the sides of the pot from its entering to its discharge end. Furthermore, to permit. such flow of products of combustion in prior constructions, the bottom flange at the entering end of the pot cannot have full bearing upon the furnace wall, and accordingly the products of combustion contact directly with a portion of the lower and all of the upper face of this flange. In the present construction the sides 3 and 4 are provided with laterally extending flanges 69 materially above the bottom of the pot. These flanges rest upon furnace walls 70 above ports 63, and hence they are out of contact with the products of combustion and above the hottest portions of the furnace walls. Furthermore, this positioning of the supportingflanges exposes a large area of the front and bottom of pot to desired heating, and prevents the heating of other portions of the pot with an attendant advantage presently to be explained.

Between heating chambers 60 and 61 there is a furnace Wall 71 (Fig. 4) which extends upwardly to the bottom of the pot and is there sealed to prevent flow of heating gases between it and the bottom of the pot, but the top of this wall does not form a support for the bottom of the pot adjacent to it. It will be observed that by constructing the furnace and pot in the manner shown and'described, the side walls of the grease pot and the partition 6 are all freely exposed to the radiation of heat with the result that the palm oil, particularly the upper portion of it. may be continuously cooled.

In operation, when first heating the tin to the temperature required for coating, valve 65 in passageway 60 may be fully opened so that the temperature of the pot effected in chamber 60 is the same or substantially the same as that affected in chamber 61. When the tin and palm oil has been raised to, or substantialy to the required temperature, valve 65 may be closed entirely, or to such extent as is necessasry to effect a substantial drop in the temperature of heating-chamber 61 as compared to heating-chamber 60. This results in greater heating of the entering end of the pot, and in consequence of this the molten tin is caused to flow in a convection .current in a cycle substantially as indicated by the dot-and-dash line 75 in Fig. 4,-the dlrection of flow being indicated by the arrows on this line. It will be noted that the tin .fiows upwardly at the entering end of the pot, then to the right and below partition 6 into the lower portion of the grease pot, and then downwardly towards and to the bottom ofthe entering side of the pot, and that the bottom 5 of the pot continuously slopes downwardly to permit of this downward and forward flow of tin from the grease pot to the entering end of the tin pot.

As the flowing body of tin contacts with the chilled tin adjacent to flux 10 (Fi 1) small particles of tin-iron alloy by virtue of their higher temperature of solidification are entrained by the chilled tin and the tin oxide mixed with it. of chilled tin and impurities mixed with it are, during the operation of the tinning apparatus, picked up by the surface of rotating roll 50 protruding above the metal line 7 and carried to the right of this roll as viewed in Fig. 1. At this point the chilled tin and impurities mixed with it are floated from roll 50 and accumulate in a mass generally indicated at 76 in Fig. 1, the mass being confined between roll 50 and the rear of flux box 11. When a substantial amount of this The coherent layer an additional roll 53, similar to roll 50, may be arranged at. the rear of the path of the entering plates and rotated to segregate chilled tin between it and the front wall of the flux box.

In a similar manner, roll 54 at the surface of the tin in the grease box is rotated to remove chilled tin and impuritiesmixedwith 7 v n it from the path of plates emerging from the tin bath. However, I have found that, by causing the tin to flow in a convection current and by removing chilled tin and impurities at the entering side of the pot in the manner explained, there is a very small accumulation of impurities on the surface of the tin in'the grease box.

The tinning apparatus is drivem so as to pass plates into and through the flux, tin bath and palm oil at a uniform rate of speed. When they enter the tin bath they do not first pass through a large mass of chilled tin and tin oxide, as has been the case heretofore, but, because this mass is being continuously removed by the action of roll 50, the plates pass through only a very thin layer of chilled tin and impurities. This layer is so thin that substantially none of it adheres to the entering plates. They may therefore be passed through the tin bath at a higher rate of speed than heretofore. Asthe plates emerge from the tin'bath beneath the oil they first pass into the bite of tinning rolls 16, and from then into the bite of tinning rolls 17, which 'rolls progressively thin the coating. Because the plates do not have solid or substantially solid particles of tin oxide and tin iron alloy adhering to them, the pairs of tinning rolls may be set to reduce the thickness of tin coating materially below yieldsheretofore commercially obtained. In actual commercial practice of this invention I have found that coke plate having a coating as low as about one pound per base box may be produced, and that such plate has a high lustre and is free from defects. As to the lustre of any grade of plates produced according to this invention, I have found that it is materially higher than that of plates of the same grade or yield produced in the manner heretofore done. .This increase in lustre in all grades of plates is due to the substantial reheat from them, and thatonly one of thegrease pot walls is exposed to heat, which heat is much less intense than that used in heating the entering end of the grease pot. By reason of this construction of the pot and regulation of heat, the palm oil at the upper portion of the grease pot is maintained at a temperature below the melting point of tin. By thus controlling the temperature of the palm oil, the molten tin adhering to the plates as they pass beyond the upper pair of tinning rolls 17 become solidified, or partially so, before the plates enter the bite of the polishing rolls 18. Therefore the surfaces of the polishing rolls impart a high degree of polish to the coating. A further advantage in this regulation of the temperature of the palm oil in the upper portion of the grease pot is the diminu-- tion of fuming'of the oil.

While the invention in its broader aspects is unlimited to the provision of feed rolls at the entering end of the tin pot above the flux, such rolls, or equivalent mechanical feeding mechanism, are preferably used because of in creased speed attained by their use, as compared with. the manual feeding of plates. Themechanical feeding of plates uniformly into and through the tin bath is of particular advantage in the practice of this invention, because, due to the substantial absence of chilled tin, tin oxide and tin-iron alloy from the bath, plates may be passed more rapidly through the bath than is possible when, as heretofore, chilled tin, tin oxide and tin-iron alloy is present in relatively large quantities.

It will be observed that the bottom 5 of the tin pot and its front and rear walls 1 and 2 slope downwardly towards the center of the entering side of the "pot. As seen in Fig. 3, this portion of the bottom of the pot also slopes downwardly from side wall 4 to side wall 3 and terminates in a well 80. If the chilled tin and impurities mixed with it are not continuously removed from the surface of the tin bath in the manner heretofore explained, tin-iron alloy will accumulate in larger particles in the bath and will sink to the bottom of the pot. By causing the molten tin to flow in a convection current cycle in the manner heretofore explained, these larger particles of tin-iron alloy will gradually flow down the sloping walls and bottom of the pot into pit 80 in ,which there may be arranged a ladle 81 for receiving and periodically removin the thus segregated particles of tin-iron al 0 from the tin. While this is not the pre erred manner of removing tin-iron alloy from the tin, nevertheless substantial advantages arise from such removal.

According to the provisions of the patent statutes, I have explained the principle of my invention, have described the preferred mode of operation, and have illustrated and described the preferred apparatus for practicing it. However, I desire to have it understood that, within thescope of the appended claims, the invention may be practiced otherwise than herein specifically explained, and by the use of apparatus otherwise than that specifically shown and described.

I claim as my invention:

1. In the manufacture of tin plate in which plates to be coated are passed through a body of flux resting upon a bath of molten tin, the step consisting of causing the chilled tin and its content of impurities at the surface of the bath adjacent to the flux to continuously move laterally to present substantially unchilled clean molten tin to the entering plates.

2. In the manufacture of tin plate in which plates to be coated are passed through a body of flux resting upon a bath of molten tin, the method comprising causing the chilled tin and its content of impurities at the surface of the bath adjacent to the flux to continuously move laterally to present substantially unchilled clean molten tin to the entering plates, and of segregating the laterally moved tin and impurities for removal from the bath.

3. In the manufacture of tin plate in which plates are passed through a bath of molten tin, the method comprising causing the molten tin to continuously flow in a cycle in its container and segregating the impurities of the bath for removal from it at a point in the cycle of flow of the bath.

1. In the manufacture of tin plate in which plates to be-coated are passed through a body of flux resting upon a bath of molten tin, the method comprising causing the molten tin to continuously flow in a cycle in its container, such flow being upwardly below the body of flux, causing the chilled tin and its content of impurities at the surface of the bath adj acent to the flux to continuously move later ally, and segregating the laterally moved tin and impurities for removal from the bath.

5. In the manufacture of tin plate in which plates to be coated are passed through a body of flux resting upon a bath of molten tin, the method comprising causing the molten tin to continuously flow in a closed cycle in its container, such flow being upwardly below the body of flux whereby particles of tin-iron alloy contained in the tin bath are carried to and become deposited in the chilled tin below the flux, causing the chilled tin and its content of impurities adjacent to the flux to continuously move laterally, and segregating the laterally moved tin and impurities for removal from the bath.

6. In the manufacture of tin plate in which plates to be coated are passed through a bath of molten tin, the method comprising causing a convection current flow of the molten tin in a cycle in its container, and segregating the impurities of the bath for removal from it at a point in the cycle of flow of the bath.

' 7. In the manufacture of tin plate in which plates to be coated are passed through a body of flux resting upon a bath of molten tin, the method comprising causing a convection current flow of the molten tin in a cycle in its container, such flow being upwardly below the body of the flux, causing the chilled tin and its rent flow of the molten tin in a closed cycle in its container, such flow being upwardly below the body of flux whereby particles of tin-iron alloy contained in thetin bath are carried to and become deposited in the chilled tin below the flux, causing such chilled tin and its content of impurities to continuously move laterally, andsegregating the' laterally moved tin and impurities for removal from the bath.

9! In the manufacture of tin plate, the method comprising passing plates at a'uniform rate of speed into and through'a body of flux, a tin bath and a body of oil, causing the chilled" tin and itscontent of impurities at the surface of the bath ad'acent to the flux to continuously move laterally to present substantially unchilled clean tin to the entering plates, and segregating the laterally moved tin and impurities for removal from the bath.

10. In the manufacturepf tin plate, the method comprising passing plates at a uniform rate of speed into and through a body of flux, a tin bath and a body of oil, causing the molten tin to continuously fiowin a cycle in its container, and segregating the impurities of the bath for removal from it at a point in the cycle of fiow'of the bath. 11. Inthe manufacture of tin plate, the method comprising passing plates at a uniform rate of speed into and through a body of fiux, a tin bath and a body of oil, causing a convection current flow of the molten tin in a cycle in its container, such flow being upwardly below the body of the flux, causing chilled tin and its content of impurities at the surface of the bath adjacent to the flux to continuously move laterally, and segregatingfthe laterally moved tin and impurities for removal from the bath.

r12. In the manufacture of tin plate, the method comprising passing plates at auniform rate of speed into and through a body of flux, a tin bath and a body of oil, causing a convection current flow of the molten tin in a closed cycle in its container, such flow being upwardly below the body of flux whereby particles of tin-iron alloy contained in the tin bath are carried to and become deposited in the chilled tin below the flux, causing such chilled tin and its content of impurities to continuously move laterally, and segregating the laterally moved tin and impurities for removal from the bath.

13. Tin plating apparatus comprising a vpot having an entering and a discharge side, plate guiding and tinning apparatus mounted in the pot, a fluxbox at the" entering side of the pot and through which plates 'are fed into molten tin contained in the pot, a roll in the flux box at a side of the path of entering plates and partially projecting above the metal line, and means for continuously rotating said roll for moving laterally the impurities at the surface of the molten tin. v

14:. Tin plating apparatus, comprising a pot having coating apparatus mounted in it and having an entering and a discharge side and provided with a bottom sloping' continuously downwardly from the discharge to the'entering side, and means for heating the entering side of the pot to a higher temperature than the discharge side whereby molten tin in the pot is caused to flow in aconvection current cycle;

15. Tin plating apparatus comprising a pot having coating apparatus mounted in it and having an entering and a discharge side and provided with a bottom sloping continuously downwardly from the discharge to the entering side, a heating furnace beneath the pot divided into two chambers, one adjacent to the entering and the other adjacent to the discharge side of the pot, and means for efiecting greater heating in the first than in the second-mentioned chamber.

i 16. Tin plating apparatus comprising a pot having coating apparatus mounted in it and havin anentering and a discharge side and provided with a bottom sloping continuously downwardly from the discharge to the enterin side, separate heating chambers beneath t e entering and the discharge sides of the pot, means for effecting greater heating in the first than in the second-mentioned chamber, and means for varying the heating effects of the two chambers with relation to each other.

- 17. Tin plating apparatus compris ng a pot having coating apparatus mounted 1n 1t and having an entering and a dlscharge slde and provided with a bottom sloplng continuously downwardly from the discharge to the enterfrom the first-mentioned chamber pass into the second-mentioned chamber to heat the discharge side of the pot to a less extent than the entering side. 7 V

In testimony whereof, I sign my name.

SAMUEL E. DIESCHER. 

